A sample transfer mechanism, in other words robotic manipulator assembly, is used by being incorporated in various types of devices that constitute a clinical laboratory automation system (CLAS), such as an in vitro diagnostic (IVD) device and a sample transport and conveying system connected to the IVD device. Various types of tests including biochemical tests, immunological tests, hematologic tests, and polymerase chain reaction assays may be considered as specific examples of IVD. Exemplary IVD devices and their peripheral devices include sample transport and conveying systems used in clinical laboratories, and loading modules, storage modules, and centrifugal modules included in sample preprocessing systems.
The sample transfer mechanism is used for picking up a sample vessel handled by, for example, an IVD device from a holder or the like and transferring the sample vessel onto, for example, another holder or the like. The term “holder or the like” as used herein refers collectively to all parts having a function of holding the sample vessel, including at least all that is collectively called a sample carrier (a sample holder, a sample bucket, a sample rack, a sample tray) and including all that has a function of, in addition to holding the sample vessel, processing (e.g. batch type thermostat) or analyzing (e.g. absorptiometric analysis, fluorescence intensity analysis) the sample with the sample vessel held in place.
A sample transfer mechanism in other words robotic manipulator assembly, includes at least one gripper assembly, a transport mechanism (e.g. an X-Y-Z stage, a robot arm) that moves an entire chuck mechanism horizontally and vertically to a desired location, and a controller that controls the gripper assembly and the transport mechanism.
The gripper assembly includes, as an end effector, a mechanism for grasping and gripping an object (a chuck mechanism) and at least a mechanism for opening and closing the chuck mechanism.
Operation of the sample transfer mechanism is achieved, broadly, by combining basic motions including an X-Y moving motion, an accessing motion, an approaching motion, a retracting motion, an opening motion, a closing motion, a clamping motion, a releasing motion, a picking motion, and a placing motion. These motions will be defined in detail when later describing embodiments.
Recent years have witnessed appearance of, for example, an IVD device that handles a plurality of types of sample vessels and sample vessels having varying lengths are mixed together inside the IVD device. A chuck mechanism for use in such an IVD device is required to have a capability of reliably gripping and transferring the sample vessels having varying lengths. The gripping position appropriate for a specific sample vessel, however, depends on each individual sample vessel that has a unique length, a unique bottom surface shape, a unique cap shape, and the like.
Gripping the sample vessel at a position other than the appropriate gripping position poses such problems as the cap of the sample vessel being gripped (which results in only the cap being removed or unsteady gripping of picking up the sample vessel together with its cap) and a part near an opening portion in the sample vessel that is likely to be contaminated being gripped.
Depending on the length of the sample vessel, conditions are possible in which, in a picking motion, the gripping arm, finger of end effecter is opened and closed at a part of the sample vessel upward of an upper bottom of the sample vessel (specifically, the gripping arm fails to grip the sample vessel) and, in a placing motion, the sample vessel is released, though the sample vessel is not fit in the holder (specifically, the sample vessel is released in the air and falls). The term “appropriate gripping position” as used herein refers to a range on an outer surface of the sample vessel, the range satisfying at least the following conditions:
(1) With the sample vessel mounted steadily in a holder or the like, a portion exposed from the holder or the like that holds the sample vessel in place (an exposed portion);
(2) All gripping arms do not contact the holder or the like during a gripping operation; and
(3) The position is away from an area near an opening portion or a cap of the sample vessel.
A related-art technique requires that lowering and raising strokes during a picking motion or a placing motion be previously set for each length of the sample vessel so as to reach the appropriate gripping position and this setting be stored in a controller as a drive pattern. In order to determine the appropriate gripping position for each picking motion for a sample vessel, a method is taken in which the height of the sample vessel is measured or detected for each motion and, based on the result of the measurement, the drive pattern (a stoke in the Z-direction, lowering and raising speed) for an approaching motion and a retracting motion is changed. (See, for example, patent document 1.)
In view of reduction of a risk of contact between the sample vessel or the like and the gripping arm for example, common practice has it that, in related-art sample transfer mechanisms, the drive range in the vertical direction (Z-direction) during the approaching motion and the retracting motion is set such that an area in which a gripping arm 160 is likely to contact the sample vessel is minimized (specifically, an upper portion is gripped).
However, detecting the height of the vessel for each approaching motion reduces throughput of the apparatus.
Moreover, preparing a large number of drive patterns requires that a teaching motion for calibrating the approaching and retracting strokes be performed in a large number of patterns and adjusting the mechanism is likely take a lot of trouble. The “teaching motion” as used herein refers to causing a machine to store, for example, position information or a relation between an operation amount or a control amount and an actual motion of an actuator or other element, or performing calibration.
In addition, the related art offered only poor methods for avoiding the risk of contact between the gripping arm and the sample vessel; specifically, one method is to reduce mounting density of the sample vessel relative to a rack or the like, resulting in low space efficiency, and another is to detect a faulty posture of the sample vessel and thereby to correct the posture of the sample vessel through, for example, moving the gripping arm (see, for example, patent document 2), which results in low time efficiency.